The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
Known powertrain systems are configured to transfer torque from a torque-generative device through a transmission device to an output member coupled to a driveline. Some powertrain systems may be configured to transfer torque originating from multiple torque-generative devices through a multi-mode transmission device to an output member coupled to a driveline. Such powertrain systems include hybrid powertrain systems and extended-range electric vehicle systems. Control systems for operating such powertrain systems control the torque-generative devices and apply selected torque transfer elements in the transmission to transfer torque in response to operator-commanded output torque requests, taking into account fuel economy, emissions, driveability, and other factors. Exemplary torque-generative devices include internal combustion engines and non-combustion torque machines. The non-combustion torque machines may include electric machines that operate as motors or generators to generate torque input to the transmission independently of torque input from the internal combustion engine. The torque machines may react torque, i.e., transform vehicle kinetic energy transferred through the vehicle driveline to electrical energy that is storable in an electrical energy storage device in what is referred to as a regenerative operation. A control system monitors inputs from the vehicle and the operator and provides operational control of the powertrain, including controlling an engine on/off state, controlling a transmission operating state, controlling the torque-generative devices, and regulating the electrical power interchange among the electrical energy storage device and the electric machines to manage outputs of the transmission, including torque and rotational speed. Known multi-mode transmission devices employ torque-transfer clutch devices to transfer torque between the engine, the torque machines and the driveline. Operating a multi-mode transmission device includes operating in one of a plurality of transmission states including fixed gear, variable, and neutral states. Operating an engine can include operating in engine-on and engine-off states.
Control of a powertrain system includes control of the transmission to activate and deactivate the clutches to effect operation in a selected operating state and to shift between the operating states. Control of a powertrain system includes control of engine operation to effect operation in an engine-on state and an engine-off state and to shift between the states. A shift path between powertrain states may include a plurality of sequentially executed transitions between powertrain states that includes transmission shifts and engine on/off shifts. There may be multiple shift paths between an initial operating state and a target operating state in a multi-mode transmission.